linux-kernel - Re: KLOGD loops continuously calling 'syslog' system call when prink is disabled

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Message-ID: <20080619163416.57d7efc0@hack>
Date:	Thu, 19 Jun 2008 16:34:16 +0100
From:	WANG Cong <xiyou.wangcong@...il.com>
To:	"Madhu R" <tuxmadhu@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: KLOGD loops continuously calling 'syslog' system call when
 prink is disabled

On Thu, 19 Jun 2008 18:39:10 +0530
"Madhu R" <tuxmadhu@...il.com> wrote:

> Hi All,
> 
>          when I disable printk(CONFIG_PRINTK=n) in the kernel config
> (2.6.26-rc6),  the klogd  loops continuously calling the 'syslog'
> system call. It consumes 99% of the cpu time ( using 'top' command ) .
> I found similar problem in the kernel mailing list and a patch had
> gone into the mainline kernel
> http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-11/msg03317.html
> 
>          In the patch, it returns 'ENOSYS'' while calling 'syslog'
> system call if printk is disabled. So the klogd keeps on calling this
> 'syslog' and returns ENOSYS and this process takes most of the CPU
> time.
> 
> 
>          Please clarify whether I am following correct procedure or
> this is DEFAULT behavior of klogd.


IIRC, this is the fault of klogd. It doesn't check the return value
of syslog(2) (or klogclt(3), a wrapper in glibc) carefully.

If you can, please send a patch to sysklogd people.

Thanks.


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